Oil monitoring (2005-, certain markets only)

Fig 1: Identifying Oil Monitoring Input And Output Signals

Courtesy of VOLVO CARS OF NORTH AMERICA.

General

The following components are used for oil monitoring:

oil level sensor (7/166)
engine control module (ECM) (4/46)
driver information module (DIM) (5/1).

One of the advantage of always monitoring the oil level is that the driver can then be informed, via the driver information module (DIM), if the oil needs topping up.

Oil quality detection

To calculate the quality of the oil, the capacitance of the oil is gauged and then compared with the capacitance of the air. (Capacitance is the ability to store an electrical charge).

The capacitance of the oil and air is measured using both the capacitive gauge elements. The volume of contaminants in the oil increases the capacitance. This provides the electronics integrated in the oil level sensor with an oil quality dependent input signal.

Oil temperature detection

The PTC resistor integrated in the oil level sensor is used to calculate the oil temperature. The resistance of the PTC resistor changes, depending on the oil temperature. The resistance increases as the oil temperature rises. This provides the electronics integrated in the oil level sensor with a temperature dependent input signal.

Oil level detection

The electronics integrated in the sensor calculate the oil level using the obtained values for oil temperature and quality.

Temporary changes in the oil level in the oil trough must be taken into account to correctly calculate the oil level. This happens when cornering and taking hills for example. The engine control module (ECM) makes these calculations using the oil level sensor signal and a number of other parameters. These other parameters include the vehicle speed signal and the load signal.

Oil level sensor signal

The oil level sensor internally calculates the parameters for oil level, quality and temperature. A PWM signal is then generated and transmitted on a cable to the engine control module (ECM).

The PWM signal consists of a pulse train. The first pulse in the pulse train represents the oil temperature. The second pulse represents the oil level. The third pulse represents the oil quality. A change in oil level, quality or oil temperature affects the pulse ratio of the relevant pulse.